Endocrine Abstracts

Introduction: The relationship between thyroid function and obesity and associated metabolic parameters has been extensively investigated especially in patients with primary hypothyroidism on levothyroxine replacement therapy. Current data show inconsistent results possibly influenced by some patients’ characteristics such as sex, age, concomitant diseases and medications.

Objective: To assess the relation between thyroid function tests and BMI, fasting blood glucose, lipids in euthyroid premenopausal women on levothyroxine replacement and healthy women without other disorders or medication intake.

Patients and Methods: 77 women with autoimmune thyroiditis on levothyroxine treatment and 249 age matched premenopausal healthy women were included in the study. All participants had TSH level within the reference range 0.4-4.2 mIU/l. The included women did not have any other significant medical conditions, including diabetes mellitus, were not taking medications other than levothyroxine, were all premenopausal not taking estrogen-containing drugs. TSH, FT4, fasting blood glucose and lipids were investigated, BMI was calculated after height and weight measurement.

Results: Women on levothyroxine had higher levels of TSH (2.44±0.12 vs 2.00±0.05 mIU/l, P < 0.01) and FT4 (11.56±0.16 vs 10.91±0.09 pmol/l, P < 0.01) compared to healthy women. No differences between BMI and the other tested parameters were estimated between the two groups. There were no significant correlations between TSH and BMI in women with autoimmune thyroiditis, slight positive correlation with total cholesterol was identified (r=0.232, P = 0.042). FT4 levels showed significant negative correlation with total (P = 0.001) and LDL cholesterol (P < 0.001). In euthyroid control group TSH showed slight positive correlations with BMI, fasting blood glucose and LDL cholesterol. FT4 levels were negatively associated with total cholesterol (P = 0.006) and HDL cholesterol (P = 0.003). After adjustment for age there were no changes in the results in both studied groups.

Conclusion: Our results support other authors’ findings that as long as TSH is kept within the reference range there is no increased risk of obesity and metabolic complications in patients with autoimmune hypothyroidism. It even might be suggested that those women have more favorable metabolic profile because of the higher FT4 levels. Adjusting the levothyroxine dose solely to decrease TSH to low-normal values is not considered beneficial and thus is not justified.